Closed loop work station bioremediation using mini-reactor cartridges

ABSTRACT

A system for capturing and neutralizing HAP&#39;s (hazardous air pollutants) and VOC&#39;s (volatile organic compounds) at the source point by providing a closed loop remediation system which utilizes an air collection, treatment and control module containing a predetermined size bay of multiple interchangeable mini-biofilter cartridges that function to consume the pollutant and recirculate remediated air back to the source point of the pollutant. The system includes establishing a closed loop air system at a work station which generates and emits VOC&#39;s, capturing the VOC&#39;s in the air stream flow and transporting them directly into an adjacent biofilter module which contains selected microorganisms in mini-cartridges which biodegrade said VOC&#39;s and recirculates remediated air back to the source point of the pollutant.

BACKGROUND OF THE INVENTION

The present invention relates in general to a system for removal andtreatment of pollutants in air, and more specifically to a source pointclosed loop remediation system. With respect to HAP (hazardous airpollutants) and VOC (volatile organic compounds) current methods of VOCremoval include distillation; oxidation combustion ionization;biofiltration; and activated carbon adsorption. All of these methods arelarge whole-building fixed systems having high installation costs, and,with the exception of biofiltration, have high energy consumption andintroduce new pollution considerations or generate hazardous waste.

The present invention includes the use of multiple small mini-reactorcartridges to reduce installation and repair or replacement andmaintenance costs, permit incremental system expansion, and allow avariety of suitable mini-reactor based remediation technologies to beused together in series or parallel.

Present systems typically treat and exhaust an entire volume of buildingair without considering the actual pollution source and concentration,resulting in inefficient pollution removal. Furthermore, air heating orcooling of the makeup building air is required which adds to totalenergy consumed.

Biofiltration utilizes the natural process of biodegradation which inits most basic form occurs in a compost pile. Most typically,water-borne microbes consume the carbon in the organic matter of thepile, and release carbon dioxide and water. By passing an airstreamcontaining an organic vapor (HAP/VOC) containing carbons through such acompost pile, the microbes will preferentially consume the more readilyavailable carbon in the gas stream, thereby cleansing said airstream.

Notwithstanding initial installation costs, biofiltration is a provenand low energy cost, natural method of HAP/VOC remediation that has beenin commercial use in large installations both in the United States andabroad for over 15 years. In biofiltration, no secondary carbon source(natural gas) is required to maintain combustion and make up for varyingconcentrations of VOC laden air as in the most widely employed oxidationprocess; and no hazardous waste is generated as with carbon absorption;and no by-products other than water and carbon dioxide are released.Distillation is usually not economically practical due to relatively lowwork place concentrations and value of the recovered chemical.

Because of their large size and method of construction and operation,current bioremediation systems have relatively high installation,secondary energy consumption and operational costs approaching the othermethods.

Current biofiltration technology includes the use of naturallybiodegradable media such as compost and vegetation as the supportingmedia and the source of both microbes and nutrients, and has proven tohave inconsistent and relatively uncontrollable and repeatable long termfield performance.

The present invention includes complete control of the microbialenvironment with the use of stable artificial media in conjunction withcontrolled water and nutrient addition for consistent operation. Thepresent invention further includes the inoculation of said environmentwith specifically isolated and custom grown inoculate tailored to theVOC/HAP to be remediated to maintain high and consistent removalefficiency.

With respect to bioremediation, the following prior art isrepresentative of the state of the art with respect to treating HAP'sand VOC's.

U.S. Pat. No. 3,880,061 broadly relates to a contamination free workstation by providing an air stream across the work station to remove anycontaminants through filter means as shown in the figure.

U.S. Pat. No. 4,734,111 is directed to a process and apparatus forcleaning spent air or air polluted with styrene and filtering out thestyrene in an apparatus and process which uses a specific biofilterutilizing a spruce bark and microorganisms thereon to degrade thestyrene.

U.S. Pat. No. 5,409,834 relates to an invention and apparatus forremoving pollutants from a source of polluted air such as a work paintstation (see FIG. 1). Polluted air from the work station is introducedfrom a supply conduit into a wet plenum chamber which has a spray nozzlewhich sprays microbial laden liquid into the incoming polluted air.

U.S. Pat. No. 5,691,192 is related to a biological filter for removingvolatile compounds from gas emissions such as styrene. The styrene isbroken down with a fungus which is contained on a carrier or inertmaterial such as perlite. Activated carbon may also be added to themixture.

U.S. Pat. No. 5,869,323 is directed to a biofilter which uses abioreactor treatment tank comprising at least one bioreactor bed and inwhich the air filtration is conducted such that the air flow through thetank is from the top downward, with the biofiltration being conductedunder pressures of less than an ambient.

These inventions teach the conventional type of prior art systems whichare used for aerobic bioremediation in commercial plants. All the above,and this patent pertain to aerobic biofiltration wherein thebiodegradation occurs on the surface of a water film by a consortium ofaerobic microbes.

U.S. Pat. No. 6,010,900 is directed to enhancing biodegradation using abioreactor. The bioreactor contains an aqueous phase in which amicroorganism capable of degrading a sparingly soluble volatile organiccompound is contained. The patent further teaches contacting thesolution with a gas/vapor stream comprising the sparingly solublevolatile organic compound such that the soluble volatile organic issolubilized in the aqueous phase to form an enriched solution, and thenincubating the enriched solution so that the microorganism degrades thesolubilized sparingly soluble volatile organic compound therebyenhancing biodegradation. (This is an anaerobic process and is notrelated to the present invention).

It can therefore be seen from the above cited commercial practices andprior art that there is a need for a bioremediation system which reducesnatural gas and energy consumption and high fixed and operation costs ofremediation; adds efficiency, control and repeatability to thebioremenation process; and does not produce hazardous waste by-productsas is typical of the current prior art systems.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a shipableby common carrier, expandable, movable, modular components, cartridgebased closed loop system for remediation of HAP/VOC's within amanufacturing plant at the source.

It is another object of the present invention to provide an efficientbiological system which reduces HAP/VOC's to water and carbon dioxide.

It is another object of the present invention to remediate processHAP/VOC's concentration over 90%.

It is yet another object of the present invention to provide a systemfor collection and neutralizing HAP's (hazardous air pollutants) andVOC's (volatile organic compounds) at the source point.

Another object is to contain the biological eco-system in multiple smallbiofilter cartridges.

Another object is to use an artificial support media for the water filmthat supplies no naturally biodegradable matter and therefore will notdegrade or compact.

Another object is the use of specifically isolated inoculate containinghighly efficient microbe strain(s) tailored to maximally consume theVOC/HAP to be remediated.

Another object is to provide appropriate nutrient addition to enhancemicrobial growth.

Another object is to provide and maintain a suitable water film to themedia to sustain the inoculate eco-system.

Another object is to replenish the media water film by periodically anddiscontinuously bio-recirculating inoculate and nutrient laden waterthrough the media at a low flow rate.

Another object is to flush excess biomass and cleanse and reactivate themedia by periodically and discontinuously filtering and recirculatinginoculate and nutrient laden water through the media at a high flowrate.

Another object is to collect, filter, store, replenish and recirculatethe nutrient and inoculate laden water within a remediation system atthe work station.

Another object is to allow reversal of the airstream flow through thereactor cartridges.

Another object is to contain air and water functions in remediationmodules.

Another object is to allow top-to-bottom physical reversal of thereactor cartridge in the system.

Another object is to allow system reversal of the airstream directionthrough the cartridge.

Another object is to allow for series and/or parallel airflow throughmultiple cartridges.

Another object is to allow various cartridges to contain differingmedia, inoculate, and/or remediation methods.

Another object is to allow individual replacement of a single cartridgein a remediation system.

Another object is to use the mini-reactor cartridge embodiment for othergranular remediation techniques.

Another object is to include exhaust stream dehumidifcation.

Another object is to combine all remediation system functions in asingle cartridge assembly.

The present invention is directed to providing a closed loop modularremediation system which includes air collection with air and watertreatment and control and contains a predetermined size bay of multipleinterchangeable mini-biofilter cartridges that function to consume thepollutant and recirculate remediated air back to the source point of thepollutant.

In one embodiment, a closed loop air stream is established at a workstation area involving fiberglass laminating which generates and emitsthe styrene HAP, which is captured by the air stream flow whichtransports the emitted styrene directly into an adjacent biofiltermodule system as described above which contains selected microorganismsin multiple mini-biofilter cartridges which consume the styrene, andrecirculates the remediated air back to the source point of thepollutant at the work station. The air flow is continuous and the systemserves to maintain the styrene level at the work station at safe levels.

In a further embodiment, multiple sources of contaminants in a givenroom or area can be captured and treated at a single remediation stationor multiple remediation stations can be used within a given room or areato treat higher concentrations.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of these and objects of the invention,reference will be made to the following detailed description of theinvention which is to be read in connection with the accompanyingdrawing, wherein:

FIG. 1 is a front view with partial break away of a self-contained aircollection, treatment and control module containing multiple biofiltercartridges used in the system of the present invention.

FIG. 2 is a schematic side view of a self-contained single cartridgeremediating system for treating a small source.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is more fully understood with reference to thedrawings where FIG. 1 illustrates a closed loop system 10 for treating awork station area or room 12 which contains a source of pollutant suchas styrene generated from laminating with fiberglass. The closed loopducting system contains an array of interchangeable mini-biofiltercartridges 14 which contain a carrier medium 16 supporting a water filmsuitable for microorganisms or a mix of microorganisms on the carriersurface which have been selected to degrade the styrene or other VOC'sof interest. The cartridge(s) is preferentially filled with a suitableinert carrier material such as perlite or an inert synthetic materialsuch as plastic or a ceramic. A moisturized and nutrientzed airflowthrough the biofilter promotes the growth of indigenous or synthesizedmicroorganisms on the surface of the carrier material which through theaction of the microorganisms acts to biodegrade the HAP and/or VOC's ofinterest. Suitable microorganisms which can be used to promote thisdegradation include bacteria, such as Pseudomonas and Mycobacterium.Other suitable natural occurring materials which contain indigenousmicroorganisms such as compost, peat, soil, wood chips, plant residuesand tree bark may also be used or included. The reversible biofilterscontain an outer housing or shell 15 suitability made of plastic andcontain a perforated top and bottom, 18 and 20 respectively, which mayinclude a screen to allow for air flow and water flow through thebiofilter. Interconnecting ducting 22 passes a flow of contaminated airfrom the room through the bottom of the biofilters with remediated airpassing back into the room through ducting 24. Pump 25 functions torecirculate and replenish the inoculated nutrient laden water film onthe carrier material in the biofilters which enhances the action of themicroorganisms in degrading the styrene. Pump 25 preferentially drawswater from lower collection trough 28 which has received excess waterfrom the biolfilters 14. Pump 25 then recirculates the water to the topof the biofilter through water manifold 30 and nozzles 32. In FIG. 1,which is not drawn to scale, area or room 12 is depicted as grosslysmaller in size than the closed loop system 10. For example thecartridges 14 are typically about 30 inches in height and 15 inches×15inches in cross-section. The discrepancy in relative sizes is to bettershow the detail of the closed loop system.

In a further embodiment of the present invention as shown in FIG. 2, asingle independent mini-reactor cartridge 40 is illustrated. Thecartridge contains an outer housing 42 and is open at both ends 44 and46 with supporting grilles (not shown) to contain the carrier media. Thecartridge contains an upper clip-on blower housing 48 which contains anexhaust fan 50 and an exhaust port 52. The blower housing is attached tothe cartridge by latch 54 and ring seal 56. A water reservoir 58 isattached to the bottom of cartridge 40 by latch 60 and ring seal 62. Thereservoir contains water 64 and optionally a wicking humidifier filter66. In operation, air to be treated is drawn in through inlet 68 andhumidified in reservoir 58. A suitable source of microorganismscontained on a carrier media 70 in the housing degrade the VOC ofinterest as previously described herein. The arrows in the drawingdepict the flow path with the remediated air passing through media 70and exiting through exhaust port 52.

A water recirculation pump 72 and associated water transfer manifold 74may optionally be added to recirculate the microbe and nutrient ladenwater from the reservoir 58 to the top of the reactor cartridge 40.Optionally dehumidification may be required to lower exit air moisturebuildup.

A single cartridge system of the type shown in FIG. 2 was used forevaluation and testing. The mini-reactor cartridge measured 15″ squareand 30″ tall with 8-½″ square inlet and outlet grilled openings atopposite ends. The nominal inside volume of the cartridge wasapproximately 3.6 cubic feet. The cartridge with a bottom grilleinstalled, weighs approximately 16 pounds. The reactor was then loadedwith 30 pounds of coarse perlite media, for a total cartridge plus mediadry weight of about 46 pounds.

The blower housing as shown in FIG. 2 was attached to the top of thecartridge along with a water replenishment port and water recirculatinghose, and a small water recirculating submergible pump was installed inthe water reservoir. The system was assembled by placing the cartridgeon top of the water reservoir and then adding the blower housing on topof the cartridge to make up a basic system as described in FIG. 2.

The system parameters were then adjusted to achieve a 5 CFM airflowgiving a nominal 45 second empty bed dwell time. The water flow was setat a nominal flow of 8 oz./hr. to supply sufficient bed moisture in therange of 4 oz./hr. to account for evaporation due to a 40% RH ambientair, plus an additional 100% excess to maintain some trickling flowthrough the bed.

The system was then loaded with 2 gallons of inoculate and nutrientmixed in water. The inoculate used was Pseudomonas Putida which iscapable of growth on toluene and is grown on a dilute minimal mediumusing styrene as a sole carbon and energy source. The inoculate is usedin a concentration of about 10⁸ CFU/ml and introduced to the cartridgeby trickling over the perlite. The nutrient used was a common slowrelease granular garden fertilizer sold by Agway under the trade nameOsomocote.

A standard styrene source which releases 100 PPM styrene at 5 CFM wasconnected to the inlet port, and the system blower and pump were startedup. Measurements were taken with a photo-ionization detector (PID) atthe inlet and outlet of the system. Within 1 hour of startup, theaverage concentration in the outlet stream was 18 PPM, and after 24hours had dropped under 9 PPM for a 90%+ reduction in styreneconcentration.

Earlier lab tests made on a similar size configuration set to the sameairflow dwell time parameters, but using a horizontal lab reactor loadedwith oak chips and natural compost, and with no water trickling orinoculate addition achieved a 75% removal rate after 7 days ofoperation, and maintained in that range for over 2 months until the testwas terminated due to the bed drying out.

Another lab test using the same lab reactor and test setup and loadedwith oak chips, and the inoculate, had faster startup results on theorder of 4 days and better long term remediation on the order of 85%,until the natural bed settled and bed channeling occurred some timeafter 3 months. This was indicated by a decrease in remediation down to80%. Disassembly of the reactor confirmed the channeling along with somebed dryup and compaction.

A further lab test using the same lab and test setup was loaded withplastic pellets and a water pump added to recirculate the water from thebottom of the reactor to the top. The Pseudomonas Putida inoculatedescribed above was used with the addition of a slow release nutrient.Initial startup time was on the order of 2 days to reach a 80% removalrate, with 90% being reached after 4 days. The reactor efficiencycontinued to increase. Pump failure eventually occurred after another 10days at which point the removal rate was up to 94%.

It should be understood that the present invention is not to be limitedby the preferred embodiments of the mini-cartridge, which may beincreased in size up to a maximum weight and volume that can be put on apallet, moved by a factory pallet jack or fork lift, and shipped bycommon carrier. This is as opposed to current large permanent singlereactor designs requiring a pit or rigging to install.

While the present invention has been particularly shown and describedwith reference to the preferred mode as illustrated in the drawing, itwill be understood by one skilled in the art that various changes indetail and configuration may be effected therein without departing fromthe spirit and scope of the invention as defined by the claims.

1. A system which remediates pollutants and toxins on site whichcomprises: (a) a work station which generates HAP's and/or VOC's; (b) anair ducting system adjacent said work station which captures saidHAP/VOC's; (c) at least one self-contained removable biofilter cartridgepositioned adjacent to said work station, wherein said cartridgecontains a source of selected microorganisms which function to degradesaid HAP/VOC's; and wherein said cartridge comprises an outer housinghaving a pair of oppositely disposed open ends, said cartridge beingfurther positioned by insertion between a closure member which containsan exhaust port positioned at one end of said housing, and a secondclosure member in the form of a water reservoir positioned at saidopposite end of said housing with said reservoir further containing aninlet for a source of air to be treated with said inlet and said exhaustport being connected to said ducting system, and circulation meanspositioned to promote the flow of air through said system; and (d) wherein operation, captured HAP/VOC's are transported to and through said airducting system and cartridge which recirculates remediated air back tothe source point of the pollutants at said work station, and where whena given cartridge is spent or damaged from use, it may be readilyremoved from the system and a new cartridge inserted in its place. 2.The system of claim 1 in which the cartridges are positioned verticallyand water is discontinuously recirculated through the microorganisms ata slow rate.
 3. The system of claim 2 where water is periodicallyflushed through the microorganisms at a fast rate.
 4. The system ofclaim 3 where said water is filtered and recirculated.
 5. The system ofclaim 4 which uses same source of water for recirculation and flushing.6. The system of claim 1 where the gas to be remediated is selected fromthe group of HAP/VOC's including carbon in their molecular structuresuch as styrene.
 7. The system of claim 1 in which the microorganismsare at least one isolated from the group consisting of bacteria.
 8. Thesystem of claim 1 in which the cartridges are sized so as to be easilyshipped by common carrier and installed by hand or with pallet jack orfork lift.
 9. The system of claim 1 in which the remediated air isdehumidified.
 10. The system of claim 1 in which the air flow isperiodically reversed.
 11. The system of claim 1 in which the cartridgesare positioned vertically and water is trickled through themicroorganisms.
 12. The system of claim 1 in which the microorganismladen water film is supported on a carrier material.
 13. The system ofclaim 12 in which the carrier is at least one artificial materialselected from the group consisting of granular inert plastics.
 14. Thesystem of claim 12 in which the carrier is at least one artificialmaterial selected from the group consisting of granular elastomers orrubbers (i.e., tires).
 15. The system of claim 12 in which the carrieris at least one artificial material selected from the group consistingof granular minerals.
 16. The system of claim 12 in which the carrier isat least one artificial material selected from the group consisting ofcrystalline minerals.
 17. The system of claim 12 in which the carriermay include at least one natural material selected from a groupconsisting of biodegradable media such as compost, tree bark andvegetation.
 18. The system of claim 12 in which the carrier materialcomprises granular pearlite.
 19. A self contained, removable,mini-reactor cartridge suitable for use in treating air containing HAP'sand/or VOC's which comprises an outer housing having a pair ofoppositely disposed open ends, a source of microorganism which arecapable of biodegrading HAP/VOCs contained within said housing, withsaid cartridge being removeably inserted between a closure in the formof a blower housing member which contains an exhaust fan and an exhaustport positioned at one end of said housing, and a second closure in theform of a water reservoir positioned at said opposite end of saidhousing, with said reservoir further containing an inlet for a source ofair to be treated, where in operation, air to be treated is passedthrough said inlet and passed through a suitable source of saidmicroorganisms contained in said housing which degrade the said HAP'sand VOC's of interest, with said treated air being released through saidexhaust port, and where said two closure members function to support andhold said cartridge in place during use.
 20. The cartridge of claim 19where inlet air is humidified by said reservoir.
 21. A self contained,removable, mini-reactor cartridge suitable for use in treating aircontaining HAP's and/or VOC's which comprises an outer housing having apair of oppositely disposed open ends, a source of microorganism whichare capable of biadegrading HAP/VOCs contained within said housing, withsaid cartridge being removeably inserted between a closure member whichcontains an exhaust port positioned at one end of said cartridgehousing, and a second closure member in the form of a water reservoirpositioned at said opposite end of said cartridge housing, with saidreservoir further containing an inlet for a source of air to be treated,and a circulating fan positioned at said inlet end, where in operation,air to be treated is passed through said inlet and passed through saidmicroorganisms contained in said housing which degrade said HAP's andVOC's of interest, with said treated air being released through saidexhaust part, and where said two closure members function to support andhold said cartridge in place during use.